It is common for one electronic device (say, a personal computer--PC) to communicate information to an external electronic device (say, a printer) over an interconnection. Typically this interconnection is a wire cable configured for the specific purpose. One popular standard for communication between a PC and a printer is the Centronics standard. According to this standard, the information is transmitted in parallel form, so that all of the bits that make up each computer word of information are transmitted simultaneously to the external device over separate lines in the wire cable.
There are many protocols for communication between two electronic devices according to the scenario described above. Generally there is a "handshake" phase in which each of the two electronic devices confirms the presence of, and correct interconnection with, the other device. Next the device that is the source of the information prepares the first word of information to be transmitted. After the word is prepared and loaded into a data latch, the information source sends a signal to the information recipient to notify the recipient. The information recipient configures itself for receipt of the information and sends an acknowledgement signal back to the signal source. Thereafter, the first word of information is transmitted. Upon correct receipt of the word of information, the recipient sends a signal to the information source, verifying that the word was received. This process is then repeated until all of the intended information has been transmitted.
As technology has progressed, a number of different protocols have developed and so has the need for higher speed transfer of information between two electronic devices. As a result, certain standards for such protocols have been developed. As one example, they are described in "Standard Signaling Method for a Bidirectional Parallel Peripheral Interface for Personal Computers," IEEE P1284 D1.00, published in draft form on Mar. 15, 1993. This document is hereby incorporated by reference. In accordance with such standards, it is important to be able to interconnect two electronic devices regardless of their own individual protocols. Further, once the two electronic devices are interconnected, it is important that the transfer of information be as fast as possible.
Heretofore, increased information transmission speeds have been realized by using wires in the interconnecting cable for purposes other than those for which they were originally intended. For example, wires that were originally intended for the bidirectional transfer of notification and acknowledgement signals are also used to transfer additional bits of the information, thereby increasing the cable's transmission speed capability. However, this approach typically requires changes in the software (and, possibly, the hardware) of the information source and recipient devices. If the source and recipient devices are then later used in other configurations, it may be necessary to change the software or hardware again for this new use. Accordingly, it is desirable to have an apparatus and method for providing a communications capability between two electronic devices without requiring that the two devices be reprogrammed.